The subject matter of the invention is a method for the hydrometallurgical recovery of lithium from the fraction of used galvanic cells containing lithium manganese oxide.
Mobile electronic devices require increasingly powerful rechargeable batteries for self-sufficient power supply. For these purposes, lithium-ion batteries are used on account of the energy density thereof expressed in Wh/kg, cycling stability and low self-discharge. Lithium-ion batteries with transition metal oxides as active cathode material are very widespread. The active cathode material in these batteries consists of lithium transition metal oxides, from which lithium ions are released during charging and intercalated in the anode material. Of particular importance are the lithium manganese mixed oxides, which are also known in abbreviated form as manganese spinel cells or batteries. Large-format lithium rechargeable batteries are used for stationary applications (power back-up) or in the automobile field for traction purposes (hybrid drive or pure electric drive). With respect to safety in the latter applications, lithium manganese oxide batteries are recognized as being of outstanding importance. Since the amount of recyclable material contained therein grows with the size and number of the manufactured, charged and reused batteries, an economical method for recovery of the lithium within the batteries is necessary.
A method for recovery of lithium from the LiFePO4-containing fraction of shredded and sifted cells is known from the document WO 2012/072619 A1, in which the fraction containing LiFePO4 is treated with acid solution in the presence of an oxidizing agent. The dissolved-out lithium ions are separated from the undissolved iron phosphate and precipitate out as salts from the solution containing lithium. The hydrometallurgical reclamation takes place with dilute sulphuric acid accompanied by introduction of oxygen, ozone or addition of hydrogen peroxide in the temperature range of 80° C. to 120° C.
Disadvantages of this method are the high energy intensity of the extraction process, the high requirements with respect to corrosion resistance of the apparatus used and the purity of the lithium salts obtained by precipitation.